Magnetic Field Sensor with Multi-Orientation Sense Layers
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Solution Overview
Problem
Existing magnetic field sensors face challenges in achieving low power consumption and cost-effective, reliable three-axis sensing without inter-axis coupling and perming effects, especially in handheld and miniaturized applications.
Innovation Solution
A magnetic field sensor design incorporating multiple orientations of reference magnetization and out-of-plane biasing of sense layers, utilizing permanent magnet layers to generate unique bias field vectors, allowing single sensor bridges to respond to out-of-plane external magnetic fields without flux guides, thereby reducing inter-axis coupling and perming effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flux guides are used to achieve three-axis sensing capability, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent removes flux guides from the sensor structure entirely, using only magnetoresistive elements with appropriately oriented pinned layers to achieve three-axis sensing. This extraction of the flux guide component simplifies the device structure while maintaining measurement precision through direct magnetoresistive sensing in multiple axes.
Solution Approach 2:
The magnetoresistive elements serve multiple functions: they provide both the sensing mechanism and the magnetic field guidance that would traditionally require separate flux guides. By orienting pinned layers in different directions, the same element structure enables sensing along multiple axes without requiring additional flux guide components for each axis.
2Measurement precision
If multiple sensor bridges are used for multi-axis sensing, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent combines multiple sensing capabilities into a single integrated sensor bridge structure by using magnetoresistive elements with pinned layers oriented in different directions within the same bridge. This merging approach allows multi-axis sensing to be achieved with one bridge rather than requiring separate bridges for each axis, thereby reducing overall power consumption while maintaining measurement precision.
3Reliability
If permanent magnets are used for biasing, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the magnetization direction parameter of the pinned layers in the magnetoresistive elements to achieve different sensing orientations without requiring physical repositioning of permanent magnets. This parameter-based approach (changing magnetic orientation through layer design rather than physical placement) maintains sensing stability while significantly reducing manufacturing precision requirements for magnet positioning.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables ultra-low power, multiple sense axis magnetic field sensors with improved sensitivity, reliability, and cost savings by eliminating the need for flux guides and minimizing inter-axis coupling, ensuring accurate and stable Z-axis sensing.
Implementation Method 1
a permanent magnet layer spaced apart from the first and second magnetoresistive sense elements. In the absence of the external magnetic field, the permanent magnet layer magnetically biases the sense magnetization in an out-of-plane orientation
Implementation Method 2
The first and second magnetoresistive sense elements are sensitive to an external magnetic field applied along a sensing direction
Data Source
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AI summary
A magnetic field sensor comprises a sensor bridge having multiple sensor legs. Each sensor leg includes magnetoresistive sense elements, each comprising a pinned layer having a reference magnetization parallel to a plane of the sensor and a sense layer having a sense magnetization. A permanent magnet layer spaced apart from the sense elements magnetically biases the sense magnetization into an out-of-plane direction that is non-perpendicular to the plane of the sensor. The sense magnetization of a portion of the sense elements is oriented in a first direction and the sense magnetization of a different portion of the sense elements is oriented in a second direction differing from the first direction to generate two unique bias field vectors of the sense layers which enables detection of the external magnetic field in a sensing direction that is perpendicular to the plane of the magnetic field sensor without inter-axis coupling of sensor response.